I think we tend to overplay the Spain/Catalan issue. First and foremost in Spanish minds is going to be the economy, and Spain are probably the EU country most likely to take the biggest hit from Brexit. They need the EU to be strong and successful to help drive their own economy, and I'd be willing to bet that will matter more to them than paranoia about Catalonian seperatism.
As for imposing austerity, those rules are always open to interpretation. We also have no idea what Scotlands debt would actually be, given that in any seperation deal they also get a sizeable share of assets.
It has nothing to do with 'getting back at England', its about ensuring the strength and prosperity of the EU for the 27 countries remaining in it. That is far and away the biggest concern for the EU now, and I don't know why people seem to be overlooking this.